Radiation therapy (e.g., x-ray irradiation) is a widely used modality for treating cancer cells. Various protocols have been developed to treat a number of specific neoplastic conditions. These methods are based in part on selective killing of rapidly dividing cells.
Another modality for treating cancer cells is hyperthermia. By heating a target area, e.g., by use of focussed microwave radiation, ultrasound, or radiofrequency, cells can be selectively injured or killed at a solid-tumor site. Success of this type of therapy can depend in part on the poorer vascularization of some solid tumors, and therefore, the poorer ability of such cells to dissipate heat.
It is known that patients vary widely in their response to cell-damaging radiation, i.e., irradiation treatment and hyperthermic treatment. An important consideration is the ability of target cells to develop resistance, either rapidly or over an extended treatment time, to the cell-damaging energy. Hyperthermic treatment, for example, can induce heat-shock proteins that appear to protect cells from heat, possibly by preventing heat denaturation of other cellular proteins.
Because target cells can vary in their short-and long-term responses to radiation or hyperthermic treatment, it is desirable to assess the susceptibility of target cells to such treatments before treatment is initiated. Such an assessment can be useful in selecting a therapeutic regimen suited to the particular properties of the target cells.